# Copyright (c) 2007-2008 Pedro Matiello <pmatiello@gmail.com>
#                         Roy Smith <roy@panix.com>
#
# Permission is hereby granted, free of charge, to any person
# obtaining a copy of this software and associated documentation
# files (the "Software"), to deal in the Software without
# restriction, including without limitation the rights to use,
# copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the
# Software is furnished to do so, subject to the following
# conditions:

# The above copyright notice and this permission notice shall be
# included in all copies or substantial portions of the Software.

# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
# EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
# OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
# NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
# HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
# WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
# FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
# OTHER DEALINGS IN THE SOFTWARE.


"""
Miscellaneous useful stuff for python-graph.
"""

# Imports
from heapq import heappush, heappop, heapify


# Priority Queue

class priority_queue:
	def __init__(self, list=[]):
		self.heap = [HeapItem(i, 0) for i in list]
		heapify(self.heap)

	def __contains__(self, item):
		for heap_item in self.heap:
			if item == heap_item.item:
				return True
		return False

	def __len__(self):
		return len(self.heap)

	def empty(self):
		return len(self.heap) == 0

	def insert(self, item, priority):
		"""
		Insert item into the queue, with the given priority.
		"""
		heappush(self.heap, HeapItem(item, priority))

	def pop(self):
		"""
		Return the item with the lowest priority, and remove it	from the queue.
		"""
		return heappop(self.heap).item

	def peek(self):
		"""
		Return the item with the lowest priority. The queue is unchanged.
		"""
		return self.heap[0].item

	def discard(self, item):
		new_heap = []
		for heap_item in self.heap:
			if item != heap_item.item:
				new_heap.append(heap_item)
		self.heap = new_heap
		heapify(self.heap)

class HeapItem:
	def __init__(self, item, priority):
		self.item = item
		self.priority = priority

	def __cmp__(self, other):
		return cmp(self.priority, other.priority)
